Method and system of updating routing/establishing paths in a hierarchical network

ABSTRACT

A mobile unit managing network is provided which is capable of supporting a communication area being wider than ever by one highest-layer router. A radio base station transfers a path updating notification fed from a mobile terminal to a lowest-layer router. The lowest-layer router establishes a path in which a network address to the mobile terminal exists in the radio base station and transfers path information to an intermediate-layer router serving as an upward router. The intermediate-layer router establishes a path in which the network address to the mobile terminal exists in the lowest-layer router and transfers path information to the highest-layer router. The highest-layer router, when having received path information notification from the intermediate-layer router, establishes a path in which the network address to the mobile terminal exists in the intermediate-layer router.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile unit managing network and apath establishing method to be used for the mobile unit managing networkand more particularly to a method for setting up a hierarchy-typenetwork.

The present application claims priority of Japanese Patent ApplicationNo. 2003-165839 filed on Jun. 11, 2003, which is hereby incorporated byreference.

2. Description of the Related Art

In a conventional mobile unit managing network based on host routing, asshown in FIG. 4, a hierarchy-type network is set up using one unit of ahighest-layer router R1 as a root router in which each of routers Ra toRf manages a path for each of mobile terminals MN1 to MN4, as disclosedin, for example, Japanese Patent Application Laid-open No. 2002-223219(Pages 5 and 6, FIG. 1).

That is, the disclosed conventional mobile unit managing networkincludes the highest-layer router R1, intermediate-layer routers Ra andRb, lowest-layer routers Rc to Rf, radio base stations BS1 to BS8, andmobile terminals MN1 to MN4 in which the highest-layer router R1 isconnected to the routers Ra to Rf through wire and the radio basestations BS1 to BS8 are connected to mobile terminals MN1 to MN4 bywireless.

Path updating notification fed from each of the mobile terminals MN1 toMN4 is transmitted through each of the radio base stations BS1 to BS8 toeach of the lowest-layer routers Rc to Rf from where the path updatingnotification is further transmitted to the highest-layer router R1. Thehighest-layer router R1 manages only a network “xxxx::/64” and networkaddresses “xxxx::1”, “yyyy::2”, “aaaa::3”, and “bbbb::4” are assignedrespectively to the mobile terminals MN1 to MN4.

In this case, a communication route is established by the highest-layerrouter R1 so that the network address “xxxx::1” exists in theintermediate layer router Ra, and “yyyy::2”, “aaaa::3”, and “bbbb::4”exists in the intermediate router Rb.

A communication route is established by the intermediate-layer router Raso that the network address “xxxx::1” exists in the lowest-layer routerRd. A communication route is established by the intermediate-layerrouter Rb so that the network address “yyyy::2” exists in thelowest-layer router Re. A communication route is established by thelowest-layer router Re so that the network address “aaaa::3” and“bbbb::4” exist in the lowest-layer router Rf.

A communication route is established by the lowest-layer router Rd sothat the network address “xxxx::1” exists in the radio base station BS3.A communication route is established by the lowest-layer router Re sothat the network address “yyyy::2” exists in the radio base station BS5.A communication route is established by the lowest-layer router Rf sothat the communication address “aaaa::3” exists in the radio basestation BS7 and the communication address “bbbb::4” exists in the radiobase station BS8.

However, a conventional network set-up method has a problem. That is, inthe conventional network set-up method, since only the number of routesfor a mobile terminal that can be managed by a highest-layer router canbe managed by one mobile unit managing network, a wide communicationarea can not be covered. To solve this problem, a method is required inwhich when a mobile terminal moves in a wide communication area, two ormore mobile unit managing networks are set up in parallel.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention toprovide a mobile unit managing network which is capable of dispersing aload of a highest-layer router and of supporting a communication areabeing wider than ever by using one highest-layer router and a pathestablishing method using the mobile unit managing network.

According to a first aspect of the present invention, there is provideda mobile unit managing network including:

a plurality of mobile terminals;

a plurality of mobile radio base stations;

a plurality of mobile lowest-layer routers;

a plurality of mobile intermediate-layer routers;

a plurality of mobile highest-layer routers;

wherein the mobile terminals, the radio base stations, the lowest-layerrouters, the intermediate-layer routers, and the highest-layer routersare hierarchically connected to one another; and

wherein each of the intermediate-layer routers according to a networkaddress of each of the mobile terminals routes to an upward router.

In the foregoing, a preferable mode is one wherein each of thelowest-layer routers and each of the intermediate-layer routers performa path establishing process to disperse a load of each of thehighest-layer routers.

Also, a preferable mode is one wherein each of the lowest-layer routersand each of the intermediate-layer routers establishes a path to each ofthe mobile terminals and to notify path information to an upward router.

Also, a preferable mode is one wherein the establishing of a path toeach of the mobile terminals, when a radio link between each of themobile terminals and each of the radio base stations is set up,establishes a path to each of the mobile terminals in response to a pathupdating notification made by each of the mobile terminals.

Also, a preferable mode is one wherein a default router is arranged aseach of the highest-layer routers.

According to a second embodiment of the present invention, there isprovided a method for establishing a path in a mobile unit managingnetwork in which mobile terminals, radio base stations, lowest-layerrouters, intermediate-layer routers, and highest-layer routers arehierarchically connected, the method comprising:

a step of having each of the intermediate-layer routers switch an upwardrouter according to a network address of each of the mobile terminals.

In the foregoing, a preferable mode is one wherein each of thelowest-layer routers and each of the intermediate-layer routers performa path establishing process to disperse a load of each of thehighest-layer routers.

Also, a preferable mode is one wherein each of the lowest-layer routersand each of the intermediate-layer routers establish a path to each ofthe mobile terminals and notify path information to the upward router.

Also, a preferable mode is one wherein, when a radio link between eachof the mobile terminals and each of the radio base stations is set up, apath to each of the mobile terminals is established in response to apath updating notification made by each of the mobile terminals.

Furthermore, a preferable mode is one wherein a default router isarranged as the highest-layer router.

With the above configuration, a communication area being wider than evercan be supported by one highest-layer router.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages, and features of the presentinvention will be more apparent from the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic block diagram showing configurations of a mobileunit managing network according to an embodiment of the presentinvention;

FIG. 2 is a diagram showing a path established in the mobile unitmanaging network according to the embodiment of the present invention;

FIG. 3 is a sequence chart showing a path establishing operation of themobile unit managing network according to the embodiment of the presentinvention; and

FIG. 4 is a diagram showing paths established in a conventional mobileunit managing network.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Best modes of carrying out the present invention will be described infurther detail using various embodiments with reference to theaccompanying drawings.

Embodiment

FIG. 1 is a schematic block diagram showing configurations of a mobileunit managing network of an embodiment of the present invention. Asshown in FIG. 1, the mobile unit managing network of the embodiment is ahierarchy-type network which includes highest-layer routers R1 to R3,intermediate routers Ra and Rb, lowest-layer routers Rc to Rf, radiobase stations BS1 to BS8, and mobile terminals MN1 to MN4. Thehighest-layer routers R1 to R3, intermediate routers Ra and Rb, andlowest-layer routers Rc to Rf are connected to one another through wire,and the radio base stations BS1 to BS8 are connected to the mobileterminals MN1 to MN4 by wireless.

For example, the highest-layer router R1 is connected to theintermediate routers Ra and Rb through wire. The intermediate routers Raand Rb are connected to the lowest-layer routers Rc to Rf through wire.The lowest-layer routers Rc and Rf are connected to the radio basestations BS1 to BS8 by wireless. Similarly, the highest-layer routers R2and R3 are connected respectively to the intermediate-layer routers Raand Rb. The intermediate-layer routers Ra and Rb are connected to thelowest-layer routers Rc to Rf, that is, the intermediate-layer router Rais connected to the lowest-layer routers Rc and Rd, and theintermediate-layer router Rb is connected to the lowest-layer routers Reand Rf. The lowest-layer routers Rc to Rf are connected to the radiobase stations BS1 to BS8, that is, the lowest-layer router Rc isconnected to the radio base stations BS1 and BS2, the lowest-layerrouter Rd is connected to the radio base stations BS3 and BS4, thelowest-layer router Re is connected to the radio base stations BS5 andBS6, and the lowest-layer router Rf is connected to the radio basestations BS7 and BS8.

The highest-layer routers R1 to R3, intermediate routers Ra and Rb, andlowest-layer routers Rc to Rf each manage the downward paths, one byone, for the mobile terminals MN1 to MN4. In the example, thehighest-layer router R1 manages only a network “xxxx::/64”. Thehighest-layer router R2 manages only a network “yyyy::/64”. Thehighest-layer router R3 manages networks that are not managed by thehighest-layer routers R1 and R2.

The network addresses “xxxx::1”, “yyyy::2”, “aaaa::3”, and “bbbb::4” areassigned respectively to the mobile terminals MN1 to MN4. High-orderalphabets in the network addresses are called a “network prefix”(standardized by IETF (Internet Engineering Task Force)) and are usedfor identifying a specified network. In the example, the highest-layerrouter R1 manages the mobile terminal MN1. The highest-layer router R2manages the mobile terminal MN2. The highest-layer router R3 manages themobile terminals MN3 and MN4.

Upward paths are established, in advance, at the intermediate-layerrouters Ra and Rb and determine a destination out of the highest-layerrouters R1 to R3 depending on a network address of each of the mobileterminals MN1 to MN4. That is, each of the high-order routers (each ofthe highest-layer routers R1 to R3) is routed to by each of theintermediate-layer routers Ra and Rb according to a network address ofeach of the mobile terminals MN1 to MN4.

For example, a packet (not shown) fed from the mobile terminal MN1having a network address of “xxxx::1” is transferred by theintermediate-layer routers Ra and Rb to the highest-layer router R1. Apacket (not shown) fed from the mobile terminal MN3 having a networkaddress of “aaaa::3” is transferred by the intermediate-layer routers Raand Rb to the highest-layer router R3 set as a default router.

FIG. 2 is a diagram showing paths established in the mobile unitmanaging network of the embodiment of the present invention. FIG. 3 is asequence chart showing a path establishing operation of the mobile unitmanaging network of the embodiment of the present invention. The pathestablishing operation of the mobile unit managing network of theembodiment of the present invention is described.

The mobile terminal MN1, after having set up a radio link with the radiobase station BS3 (Step a1 in FIG. 3), transmits a path updatingnotification of a network to the radio base station BS3 (Step a2 in FIG.3). The radio base station BS3 transfers the path updating notificationfed from the mobile terminal MN1 to the lowest-layer router Rd (Step a3in FIG. 3).

The lowest-layer router Rd, after having established a path in which anetwork address of “xxxx::1” addressed to the mobile terminal MN1 existsin the radio base station BS3 (Step a4 in FIG. 3), transfers the pathinformation notification to the intermediate-layer router Ra serving asan upward router (Step a5 in FIG. 3).

The intermediate-layer router Ra establishes a path in which the networkaddress “xxxx::1” addressed to the mobile terminal MN1 exists in thelowest-layer router Rd (Step a6 in FIG. 3). In the example, since anetwork to which the network address of “xxxx::1” belongs is“xxxx::/64”, the intermediate-layer router Ra transfers the above pathinformation notification to the highest-layer router R1 (Step a7 in FIG.3).

The highest-layer router R1, when having received the path informationnotification from the intermediate-layer router Ra, establishes a pathin which the network address of “xxxx::1” addressed to the mobileterminal MN1 exists in the intermediate-layer router Ra (Step a8 in FIG.3).

When a radio link between the mobile terminals MN2 to MN4 and the radiobase stations BS5, BS7, and BS8 is set up, by using the same procedureas described above, as shown in FIG. 2, paths to the highest-layerrouters R2 and R3 are established.

Thus, in the hierarchy-type mobile unit managing network, when the radiolink between the mobile terminals MN1 to MN4 and the radio base stationsBS3, BS5, BS7, and BS8 is set up, by having each of the lowest-layerrouters Rc to Rf and each of the intermediate-layer routers Ra and Rbestablish paths to each of the mobile terminals MN1 to MN4 and bynotifying the path information to the upward router, a load of each ofthe highest-layer routers R1 to R3 can be dispersed and a communicationarea being wider than ever can be supported by one highest-layer router.As a result, in the embodiment, even if each of the mobile terminals MN1to MN4 moves to a wider communication area, continuous communicationsare made possible.

According to the embodiment of the present invention, since a mobileterminal not scheduled to be managed by the mobile unit managing networkcan be managed, a mobile terminal that has moved from abroad can be alsomanaged in the same configurations of the network in the same manner asabove.

It is apparent that the present invention is not limited to the aboveembodiments but may be changed and modified without departing from thescope and spirit of the invention. For example, in the above embodiment,each of the lowest-layer routers Rc to Rf, each of theintermediate-layer routers Ra and Rb, and each of the highest-layerrouters R1 to R3 manage two pieces of lower-end mobile terminals,however, the number of routers in each hierarchical layer or the numberof hierarchical layers may be increased. Moreover, according to thepresent invention, the number of routers that can be connected by eachof the routers R1 to R3 and Ra to Rf and the number of radio basestations may be increased and the communication method for the radiolink between the mobile terminal and the radio base station is notlimited.

What is claimed is:
 1. A system of updating routing paths in ahierarchical network comprising: a plurality of mobile terminals; aplurality of intermediate-layer routers; and a plurality ofhighest-layer routers; wherein said mobile terminals, and saidintermediate-layer routers are hierarchically connected to one another,each said intermediate-layer router being connected to each saidhighest-layer router, said highest-layer routers each manage a specifiednetwork of hierarchy, and wherein said intermediate-layer routers eachmanage network addresses which are assigned respectively to said mobileterminals hierarchically connected thereto, and identify a highest-layerrouter of the plurality of highest-layer routers, based on each of saidnetwork addresses, to route to an upward router, each said networkaddress including address of said mobile terminal and networkidentifying information for identifying said specified networkassociated with a highest-layer router of the plurality of highest-layerrouters.
 2. The system of updating routing paths in a hierarchicalnetwork according to claim 1, further comprising a plurality of radiobase stations, each of which is connected to each of saidintermediate-layer routers, wherein each of said mobile terminals setsup a radio link with each of said radio base stations.
 3. The system ofupdating routing paths in a hierarchical network according to claim 2,further comprising a plurality of lowest-layer routers, each of which isconnected between a plurality of said radio base stations and thecorresponding intermediate-layer router, wherein each of saidlowest-layer routers and each of said intermediate-layer routers performa path establishing process to disperse a load of each of saidhighest-layer routers.
 4. The system of updating routing paths in ahierarchical network according to claim 3, wherein each of saidlowest-layer routers and each of said intermediate-layer routersestablishes a path to each of said mobile terminals and notifies pathinformation to an upward router.
 5. The system of updating routing pathsin a hierarchical network according to claim 4, wherein saidestablishing the path to each of said mobile terminals, when a radiolink between each of said mobile terminals and each of said radio basestations is set up, establishes a path to each of said mobile terminalsin response to a path updating notification made by each of said mobileterminals.
 6. The system of updating routing paths in a hierarchicalnetwork according to claim 1, wherein at least one default router isdefined among said plurality of highest-layer routers.
 7. method forupdating routing paths in a network including a plurality of mobileterminals, a plurality of intermediate-layer routers, and a plurality ofhighest-layer routers, the method comprising: a step of connectinghierarchically said mobile terminals, and said intermediate-layerrouters to one another, each said intermediate layer router beingconnected to each of said highest-layer routers; a step of having saidhighest-layer routers each manage a specified network of hierarchy-type;and a step of having said intermediate-layer routers each manage networkaddresses which are assigned respectively to said mobile terminalshierarchically connected thereto, and identify a highest-layer router ofthe plurality of highest-layer routers, based on each of said networkaddresses, to route to an upward router, each said network addressincluding address of said mobile terminal and network identifyinginformation for identifying said specified network associated with ahighest-layer router of the plurality of highest-layer routers.
 8. Themethod for updating routing paths in a network according to claim 7,wherein said network further comprises a plurality of radio basestations, each of which is connected to each of said intermediate-layerrouters, wherein each of said mobile terminals sets up a radio link witheach of said radio base stations.
 9. The method for updating routingpaths in a network according to claim 8, wherein said network furthercomprises a plurality of lowest-layer routers, each of which isconnected between a plurality of said radio base stations and thecorresponding intermediate-layer router, wherein each of saidlowest-layer routers and each of said intermediate-layer routers performa path establishing process to disperse a load of each of saidhighest-layer routers.
 10. The method for updating routing paths in anetwork according to claim 9, wherein each of said lowest-layer routersand each of said intermediate-layer routers establishes a path to eachof said mobile terminals and notifies path information to an upwardrouter.
 11. The method for updating routing paths in a network accordingto claim 10, wherein said establishing the path to each of said mobileterminals, when a radio link between each of said mobile terminals andeach of said radio base stations is set up, establishes a path to eachof said mobile terminals in response to a path updating notificationmade by each of said mobile terminals.
 12. The method for updatingrouting paths in a network according to claim 7, wherein at least onedefault router is defined among said plurality of highest-layer routers.13. A system of updating routing paths in a hierarchical networkcomprising: a plurality of mobile terminals; a plurality ofintermediate-layer routers; and a plurality of highest-layer routers;wherein said mobile terminals, and said intermediate-layer routers arehierarchically connected to one another, each said intermediate-layerrouter being connected to each said highest-layer router, saidhighest-layer routers each manage a specified network of hierarchy, andwherein each of said intermediate-layer routers comprises a unit tomanage network addresses which are assigned respectively to said mobileterminals hierarchically connected thereto, and identify a highest-layerrouter of the plurality of highest-layer routers, based on each of saidnetwork addresses, to route to an upward router, each said networkaddress including address of said mobile terminal and networkidentifying information for identifying said specified networkassociated with a highest-layer router of the plurality of highest-layerrouters.
 14. The system of updating routing paths in a hierarchicalnetwork according to claim 13, further comprising a plurality of radiobase stations, each of which is connected to each of saidintermediate-layer routers, wherein each of said mobile terminals setsup a radio link with each of said radio base stations.
 15. The system ofupdating routing paths in a hierarchical network according to claim 14,further comprising a plurality of lowest-layer routers, each of which isconnected between a plurality of said radio base stations and thecorresponding intermediate-layer router, wherein each of saidlowest-layer routers and each of said intermediate-layer routers performa path establishing process to disperse a load of each of saidhighest-layer routers.
 16. The system of updating routing paths in ahierarchical network according to claim 15, wherein each of saidlowest-layer routers and each of said intermediate-layer routerscomprise a means to establish a path to each of said mobile terminalsand to notify path information to an upward router.
 17. The system ofupdating routing paths in a hierarchical network according to claim 16,wherein said means to establish the path to each of said mobileterminals, when a radio link between each of said mobile terminals andeach of said radio base stations is set up, establishes a path to eachof said mobile terminals in response to a path updating notificationmade by each of said mobile terminals.
 18. The system of updatingrouting paths in a hierarchical network according to claim 13, whereinat least one default router is defined among said plurality ofhighest-layer routers.
 19. The system of updating routing paths in ahierarchical network according to claim 1, wherein each of saidintermediate-layer routers routes to an upward router based oncorrespondence between address of the mobile terminal and a networkprefix assigned to a highest layer router of the plurality ofhighest-layer routers, each said network address including the addressof the mobile terminal and the network prefix as said networkidentifying information.
 20. The method for updating routing paths in anetwork according to claim 7, wherein each of said intermediate-layerrouters routes to an upward router based on correspondence betweenaddress of the mobile terminal and a network prefix assigned to ahighest layer router of the plurality of highest-layer routers, eachsaid network address including the address of the mobile terminal andnetwork prefix as said network identifying information.
 21. The systemof updating routing paths in a hierarchical network according to claim1, wherein each highest-layer router of the plurality of highest-layerrouters manages a logical network, the network address of each mobileterminal corresponding to the logical network.
 22. The method forupdating routing paths in a network according to claim 7, wherein eachhighest-layer router of the highest-layer routers manages a logicalnetwork, the network address of each mobile terminal corresponding tothe logical network.